It is also worth pointing out that people do not carry around ‘extra’ protein stores held in reserve doing nothing — just waiting to fill in for the day we don’t eat enough dietary protein.
There is a small storage reservoir of protein in the body called the labile store of protein, which is roughly 1% of our total lean mass. But it’s not in a purely storage molecules like triglycerides, glycogen, or betahydroxybutyrate (respectively storing fatty acids, glucose and acetoacetate), it’s mostly protein structures deployed for uses that can be easily redeployed … eg: circulating lipoproteins like albumin, and LDL, and old tissue just waiting for a quiet period to undergo normal apoptosis.
We also have the ability to make many amino acids from metabolic raw materials, reclaiming nitrogen from circulating levels of urea. So in the initial days after a fast our net nitrogen loss will be reduced as we become nitrogen sparing.
- Rabast et al, 1981.
Total fasting was compared with a 300 kcal/day very low calorie diet providing 56 g protein and 12 g carbs in 14 healthy obese patients, selected as matched pairs, over a period of 28 days. The weight loss was significantly greater during fasting than during the VLCD (16.5 kg vs. 12.7 kg). The basal metabolic rate showed a significant decrease (25 per cent) during total fasting, but was unchanged with the VLCD.
Dr Phinney is right that healthy obese people who fast for 28 days have been observed to eventually see a 25% reduction in resting metabolic rate [ https://www.ncbi.nlm.nih.gov/pubmed/7275468 ]. I suspect a lean person who fasts would see something similar after their circulating elastic capacity is drawn down - say after an 18 hour fast.
A type 2 diabetic with adequate body fat reserves who fasts may well have a greater energy surplus, as their access to their stored energy is no longer constrained by elevated insulin. I’d like to see some metabolic cart studies into fasting subjects (lean insulin sensitive, and overweight insulin resistant) and put some real data and contexts on this question of what happens to your resting metabolic rate when you fast and how that changes over time.
Is Dr Fung correct that metabolic rate increases over the first few days to increase the likelihood of a successful hunt? And is Dr Phinney correct that the body adapts over longer periods to become energy sparing?
I didn’t know about [ https://www.ncbi.nlm.nih.gov/pubmed/2104036 ] which suggests based on Dr Phinney’s interpretation of his own study that a protein level of 1.5 g/kg is more protective of function than 1.2g/kg
Compared to baseline, VO2max and peak quadriceps strength declined on the 1.2 g/kg protein dose, whereas both of these functions were preserved at the 1.5 g/kg level.
I found it interesting that the lower protein arm also had 3 times the carbohydrates of the higher protein arm (30 vs 10g/day) and while the statistical significance for the results of the lower protein higher carb arm were just significant (VO2 max 2.44 - 2.06 l/min) the results for the higher protein lower carb arm were just below the level of significance (2.16 - 2.01 l/min). With the carbohydrate confound and the closeness of the results I suspect his interpretation may be a little generous to his narrative.
The amount of lean tissue you have is a strong determinant of your resting metabolic rate. Interpretation: your total muscle mass is your furnace – the more muscle you have the faster you can burn energy.
Interestingly Dr Phinney did one of the experiments that shows that resting metabolic rate is dynamic and determined by energy budget (which will include supplying energy to lean mass). [ http://www.metabolismjournal.com/article/0026-0495(88)90011-X/abstract ] Where he locked 12 obese women in a metabolic ward, fed them slightly hypocalorically so they were under modest energy constraints - then had half of them run on a treadmill up to 2 hours, and the others just sit on the couch watching TV. After 5 weeks he weighed them and the couch potatoes lost a non significant amount more weight because the exerciser’s metabolic rates were down regulated for the 20 hours in the day when they were not on a treadmill to account for the increase in exercise demand for energy.
In general I agree with Dr Phinney that not getting adequate protein is a serious problem. He mentioned to me when he was in Sydney recently - In the 1970s there was a liquid protein fast (basically jello shots) that was nutritionally inadequate and killed several people but because they coincidentally get people into a state of ketosis - THAT damaged the reputation of ketogenic diets for decades and dried up all funding right at the most important phase of his career. So I get why he is concerned. He’s too old to have to go into the wilderness for 4 decades again.
But there is also the problem of diets that advocate unsafe levels of too much protein. There are plenty of people around the internet recommending eating 4.4g/kg LBM and up … and there is research [ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC333026/ ] showing that healthy people can only deaminate about 3.31g/kg LBM of protein a day before they saturated their ability to dispose of the ammonia … and that has killed 2 people in 2017 alone.
This is why I believe that Ketogenic diets should actively avoid being associated with high protein fads. Diabetics who need the option of ketogenic diets to reverse their disease also can not go back into the wilderness for 4 decades.
) There is a woeful lack of research and knowledge about it, to be sure. At the same time, trials are being done on drugs that start autophagy in the body, due to their promise of being cancer treatments, etc.
I did not know that ketosis had anything specifically to do with autophagy, other than presumably occurring at the same time if one is burning fat. In reading about it, you are definitely right - ketones do stimulate at least one type of autophagy - called “chaperone-mediated autophagy.”
. Best of my current knowledge there are three distinct types of autophagy. I also am very interested in apoptosis but have not really did a literature review of this and fasting.